Radio frequency distribution system for trains



A. R. HQPKINS RADIO FREQUENCY DISTRIBUTION SYSTEM FOR TRAINS July 16,1935.

Filed May 10, 1932' INVENTOR I ALVA Magus I I I M ATTORNEY Patented July16, 1935 RADIO FREQUENCY DISTRIBUTION SYSTEM FOR. TRAINS Alva R.Hopkins, Merchantville, N. 1., assignor to Radio Corporation of America,a corporation of Delaware Application May 10, 1932, Serial No. 610,427

4 Claims.

My present invention relates to radio broadcast reception anddistribution, and more particularly to a novel and improved system ofreceiving and distributing radio broadcast programs through the cars ofa train.

The present system of radio broadcast reception distribution for trainsinvolves many practical features, and offers numerous advantages over'atrain radio broadcast reception and distribution system whichnecessitates especial train line connections between cars. This isespecially true in the case of systems requiring special train lineconnections in the making up of trains, when not all of the cars areradio equipped.

It may be stated that it is one of the main objects of the presentinvention to provide a system wherein regular broadcast programs arereceived on trains and distributed to individual cars by means ofultra-high frequency waves, the individual cars being equipped withshort wave receivers and audio frequency amplifiers with suificientoutput and proper volume levels to supply the necessary power per car.

Another important object of the present invention is to provide in atrain a broadcast receiver, connected with a suitable antenna, and highfrequency transmitter with its antenna, or loop, the receiver andtransmitter being installed on either a club car or observation car, andthe transmitter being adapted to distribute programs to all properlyequipped cars in the train regardless of the arrangement of the cars.

Another object of the present invention is to provide a centralizedradio system for a train wherein there is provided a broadcast receiverand an ultra-high frequency transmitter in a master receiver car of thetrain, the broadcast receiver supplying audio frequency power to variousoutlets in the master receiver car, and also functioning to modulate thetransmitter, the latter being utilized to rebroadcast the broadcastsignals for pick-up by other cars in the same train, each radio equippedcar in the train being provided with an ultra-high frequency receiver,and an audio amplifier system to supply ample audio power to the variousoutlets in the car, such outlets being loudspeakers, headphones, orradio pillows.

Still another object of the present invention is to provide a programreception and distribution system for a train of cars wherein thenecessity of special train line connections is eliminated, and whereinpower is supplied to the equipment in each car from the usual directcurrent lighting circuit of the respective cars thereby dividing theload on the train batteries, and wherein the individual units for eachcar are small, portable for servicing and replacement, and easilylocated in the cars.

And still other objects of the present invention 5 are to improvegenerally the simplicity and emciency of radio broadcast programs anddistribution systems for trains, and to particularly provide a system ofthis type which is not only economical, durable and reliable inoperation, but economically installed and serviced.

The novel features which I believe to be characteristic of my inventionare set forth in particularity in the appended claims, the inventionitself, however, as to both its organization and method of operationwill best be understood by reference to the following description takenin connection with the drawing in which I have indicateddiagrammatically one circuit arrangement whereby my invention may becarried into effect.

Referring now, to the drawing, there is shown in conventional form atrain comprising at least two cars I, 2, the dotted lines 3 between thetwo cars representing additional cars It is to be clearly understoodthat the car 2, the master receiver, car, need not be disposed at theend of a train, but may be a club car, an observation car, the diningcar or any other car on the train which possesses sufllcient space tohouse a broadcast receiver 4, an audio frequency amplifier 5, and ashort wave transmitter 6.

The broadcast receiver 4 is preferably of the superheterodyne typeprovided with automatic volume control in order to maintain asubstantially constant level during operation. Any superheterodynereceiver of this type may be employed for this purpose, it beingbelieved unnecessary to show the details of such a receiver since thoseskilled in the art are well acquainted with its constructional details.However, for the purposes of illustration, a superheterodyne receiver ofthe type disclosed by Friis in U. S. Patent 1,675,848 of July 3, 1928may be employed for this purpose. The audio frequency amplifier 5 may bethe usual audio frequency amplifier of the receiver l, or it maycomprise an independent power amplifier device.

The short wave transmitter 6 is an ultra-high frequency transmitteroperating on the six meter band, and need not be described in anyfurther detail than to point out that it may be of any well knownconstruction, and includes a dipole, or linear, radiator l. The masterreceiver car 2 is equipped with a suitable outside antenna 8, connectedby a lead-in wire 9 to the input side of the broadcast receiver 4, itbeing understood, of course, that the broadcast receiver has the lowpotential side of its input grounded in any desired manner, as to theframework of the car.

Power is supplied to the equipment in the master receiver car from theconventional 32 volt direct current lighting source 9 of the car,through conductors 9, it being noted that the circuits between thesource 9 and the lighting source of the car are omitted. A powerconverter may be used, and in that case would be connected in the powersupply leads connecting the receiver units and the lighting circuit.This converter may be either a dynamo for generating the required platevoltage, a motor-generator set, or a thyratron inverter to generate a 60cycle alternating current voltage.

The output of the audio frequency amplifier 5 is distributed to variousreproducers disposed within the master receiver car, and another portionof the audio output is impressed, through conductors I0, upon theshort-wave transmitter 6 whereby the audio output of the amplifier 5 isemployed to modulate the transmitter 6, the latter then rebroadcastingthe signals for pick-up by the other cars in the same train.

The remaining cars of the train, that is to say, the cars other than themaster receiver car 2, may be each equipped with a short wave receiverH. Each receiver i l is provided with a dipole, or linear, collector 12,it being understood that the short wave receiver is designed to select,detect and amplify the energy rebroadcast from the short wavetransmitter B. In other words, the receiver I i is preferably fixedlytuned to the frequency of the short wave transmitter 6, to wit: in thesix meter band. Any desired type of short wave receiver, which isadapted to operate in the six meter band, may be employed, it beingbelieved unnecessary to go into the details of such a receiver, sincethose skilled in the art are well aware of such construction.

The direct current lighting source 9 of each car, as pointed outheretofore, is utilized for energizing the various circuits of eachshort wave receiver i l either directly or by use of a suitable inverterwhere higher voltage is desired, and the audio output of each receiveris supplied to various reproducers disposed in each car. It is to beunderstood that suitable audio frequency amplification is provided inconjunction with each receiver H so that operation of the variousreproducers in each car is readily possible. Itwill be noted that eachof the cars, including the master receiver car, includes loudspeakers13, the latter being adapted for use in compartments and public spaces.

Furthermore, headphones H are provided in the various cars for use inparlor cars and Pullman seats, or in general in any location whereindividual reception is desirable. It will also be noted that theloudspeakers are disposed on a line i5, which line is distinct from theheadphone line IS. The headphone line 16 may also include radio pillowdevices I1. Such radio pillow devices usually comprise an inflatedpillow, or a pillow filled with rubber padding in the center of whichpillow is disposed a headphone so that reception can be had while aperson is resting his head against the pillow. Such a device isdisclosed and claimed in application Serial No. 412,044 filed December6, 1929 by E. J. Quinby.

It is to be clearly understood that as many headphones of the head settype or of the radio pillow type, as are desired, may be employed oneach of the headphone lines I6 in each car of the train. The radioequipment comprising the units 4, 5 and 6 of the master receiver car,and the short wave receiver H in each of the remaining cars ispreferably made small, and encased in sturdy metal cabinets of suitableshape whereby they may be disposed in the linen closets, or other out ofthe way places in the cars of a train.

These units are preferably more or less portable and detachable forreplacement and servicing. The output to the loudspeaker lines [5 andthe headphone line l6 should be sufficient, and at the proper volumelevel, to supply the necessary audio power per car. In other words, theloudspeaker lines have their inputs arranged so that the proper volumelevel is maintained for proper loudspeaker operation, while theheadphone lines l6 are maintained at the proper volume level forheadphone operation.

The operation of the above system is believed to be clear from theforegoing description and the accompanying drawing. It will be obviousto those skilled in the art that there has been disclosed in the presentapplication a method of receiving and distributing broadcast programs ina system wherein a broadcast receiver, with suitable antenna, and a highfrequency transmitter with its radiator is installed on either a clubcar or observation car, or any other master receiver car, the masterreceiver car equipment being adapted to distribute programs to allproperly equipped cars in the train regardless of the arrangement of thecars.

Local announcements can be made over the system by connecting amicrophone to the input of the audio amplifier 5 in the master car. Thiswould modulate the transmitter, and would be picked up simultaneously onall receivers. With practically the same arrangement, a phonographelectric pick-up can be substituted for the microphone and therebyenable recorded programs to be distributed throughout the train.

While I have indicated and described one arrangement for carrying myinvention into effect, it will be apparent to one skilled in the artthat my invention is by no means limited to the particular organizationshown and described, but that many modifications may be made withoutdeparting from the scope of my invention as set forth in the appendedclaims.

What I claim is:

1. In combination in a program distribution system for a train, areceiver tunable to standard broadcast frequencies disposed within oneof the cars of said train and adapted to select a desired broadcastprogram, an ultra-high frequency transmitter arranged to generatecurrents having a wave length of the order of 6 meters disposed withinsaid car and being arranged to have oscillations generated by itmodulated by the output of said broadcast receiver, said transmitterincluding a radiator located entirely within said car for broadcastingthe modulated ultra-high frequency oscillations to the remaining cars ofsaid train, a receiver disposed in one or more of the remaining cars ofsaid train, the receiver being tuned to the frequency of oscillationsradiated by said transmitter, each of said ultra-high frequencyreceivers including a. collector disposed within the same car, and aplurality of reproducers connected to the output of each of saidultra-high frequency receivers, and means for energizing the circuits ofeach ultra-high frequency receiver from the direct current lightingsource of each of said remaining cars.

2. In combination in a program distribution system for a train of cars,a radio receiver having an input circuit tunable over the broadcastingfrequency range disposed within one of said cars, an antenna mounted onthe roof of said car and having a length substantially equal to that ofsaid car, a lead connecting said antenna to an input terminal of saidreceiver, an audio frequency amplifier connected to said receiver, apair of leads connected to the output of said amplifier, a plurality ofloudspeakers connected across said leads, a transmitter disposed withinsaid car arranged to generate wave lengths of the order of 6 meters,means coupling said transmitter to said audio amplifier, a dipoleantenna disposed within said car and connected to said transmitter forbroadcasting the modulated high frequency oscillations to the remainingcars of said train, receivers disposed within other cars of said trainand tuned to the frequency radiated by said transmitter, each saidreceiver comprising a dipole antenna disposed within the same 3. Thecombination defined in the preceding claim in which at least one of saidlast named audio amplifiers has a pair of output terminals energized ata low volume level, a pair of leads connected to said terminals and aplurality of telephone receivers disposed adjacent the seats of said carand connected to said leads.

4. A method of distributing broadcast programs through a train of cars,which consists in detecting and amplifying a desired audio frequencymodulated broadcast program in one of the cars of said train, supplyingthe amplified audio frequency energy to a plurality of reproducers insaid car, producing oscillations having a wave length of the order of 6meters, modulating said oscillations with a portion of said amplifiedaudio frequency energy, radiating the modulated oscillations to theremaining cars of said train, 001- lecting the radiated modulatedoscillations in at least one of said remaining cars of said train,detecting and amplifying at audio frequency the collected oscillationsin said one car and supplying a plurality of reproducers with theamplified energy whereby the latter are caused to simultaneouslyreproduce the same modulations reproduced in the reproducers of saidfirst mentioned car.

ALVA R. HOPKINS.

